Detection of 3-Iodothyronamine in Human Patients: A Preliminary Study

Context and Objective: The primary purpose of this study was to detect and quantify 3-iodothyronamine (T(1)AM), an endogenous biogenic amine related to thyroid hormone, in human blood. Design: T(1)AM, total T-3, and total T-4 were assayed in serum by a novel HPLC tandem mass spectrometry assay, which has already been validated in animal investigations, and the results were related to standard clinical and laboratory variables. Setting and Patients: The series included one healthy volunteer, 24 patients admitted to a cardiological ward, and 17 ambulatory patients suspected of thyroid disease, who underwent blood sampling at admission for routine diagnostic purposes. Seven patients were affected by type 2 diabetes, and six patients showed echocardiographic evidence of impaired left ventricular function. Interventions: No intervention or any patient selection was performed. Main Outcome Measures: serum T(1)AM, total and free T-3 and T-4, routine chemistry, routine hematology, and echocardiographic parameters were measured. Results: T(1)AM was detected in all samples, and its concentration averaged 0.219 +/- 0.012 pmol/ml. The T(1)AM concentration was significantly correlated to total T-4 (r = 0.654, P < 0.001), total T-3 (r = 0.705, P < 0.001), glycated hemoglobin (r = 0.508, P = 0.013), brain natriuretic peptide (r = 0.543, P = 0.016), and gamma-glutamyl transpeptidase (r = 0.675, P < 0.001). In diabetic vs. nondiabetic patients T(1)AM concentration was significantly increased (0.232 +/- 0.014 vs. 0.203 +/- 0.006 pmol/ml, P = 0.044), whereas no significant difference was observed in patients with cardiac dysfunction. Conclusions: T(1)AM is an endogenous messenger that can be assayed in human blood. Our results are consistent with the hypothesis that circulating T(1)AM is produced from thyroid hormones and encourage further investigations on the potential role of T(1)AM in insulin resistance and heart failure. (J Clin Endocrinol Metab 97: E69-E74, 2012)